Marek’s disease is a common disease that is not treatable in poultry. It is caused by herpes virus and associated with high mortality
Like many herpes viruses, once an animal becomes infected, it will be infected for life. Not all infected birds, however, will get sick. The percentage of clinically sick birds in a flock depends on the strain of virus (some virus strains are more virulent than others) and the breed of bird. The percentage of illness and death in a flock can be anywhere from 1% to up to 50%. The clinical disease is typically seen between 6 weeks to 24 weeks of age. But Marek’s Disease can develop in older birds as well.
HOW DO BIRDS CONTACT MAREK’S?
The virus is very contagious and spread through direct contact or by inhaling virus Laden dander (birds to birds aerosols and secretions) and indirect contact (when birds have contact with contaminated materials). The virus concentrate in feathers follicless and can also be shed in dander.
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One way that Marek’s Disease is not acquired is through the hatching egg. Even if the breeders are infected, the chicks will hatch clean if they do not come into contact with the dander.
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Marek’s disease- causing virus particles can survive for months in chicken house, dust and litter for months and years even when the birds are gone.
SYMPTOMS OF MAREK’S DISEASE
- Infected birds commonly present with unilateral (one sided) paralysis
- Inflammation and tumors in nerves, internal organs including the heart, liberal, ovary and lung
- Affected birds die of starvation, inability to reach feed or tramplimh by other birds.
- Swollen feather follicles(bumps) on the skin that can form Cristy scabs.
- Gray eye color and misshapen iris due to infiltration of lymphocytes in the eye
- Weight loss
HOW TO PREVENT MAREK’S DISEASE
- Vaccination of day old baby chicks is the most dependable way to prevent the clinical disease. Birds must get the vaccine before they are exposed to the virus. Keep chicks from other birds until immunity has developed (minimum 2 weeks).
- Only purchase birds that have been vaccinated
- Maintain good sanitation and ventilation in the poultry house.
- Practice good biosecurity
- Observe the flock for any signs of the disease and isolate any birds that is suspected of being affected.
HOW TO KNOW IF YOURS BIRDS HAS MAREK’S DISEASE
Diagnosis of Marek’s Disease is by typical symptoms, necropsy(autopsy of dead birds) , and biopsy examination of the tissues. Most diagnostic animal labs can test for this disease in necropsy specimens.
TREATMENT OF MAREK’S DISEASE
There is no treatment available, prevention is the key; it’s best to vaccinate all birds for MAREK’S disease at one day of age or purchase pre vaccinated birds from hatcheries.
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Common misperceptions about Marek’s Disease
- Mix turkeys and chicks together to prevent Marek’s Disease so the chickens will be exposed naturally to turkey herpes virus. This is not correct! Not only will the chickens not get Marek’s Disease protection, but turkeys might be exposed to other common chicken diseases such as Mycoplasma and Blackhead.
- Don’t vaccinate birds so that the survivors will become resistant. Genetic disease resistance takes decades to develop and so far, has not been successful with Marek’s Disease. If it were successful, one would think the commercial chicken genetic companies would have developed resistant chickens by now.
- Only vaccinate a few birds and the vaccine will leak and protect the other chickens. This is incorrect. Every bird needs to get a full dose of vaccine before they become exposed to the actual disease-causing virus. This is the only way to achieve protection.
- Don’t vaccinate birds because this vaccine is dangerous and might make the chickens ill. If careful mixing of the vaccine in a sanitary manner is not followed, the birds may get a bacterial infection. Wash hands, use a sterile needle, and avoid touching the needle with hands or any soiled object. Use only commercial vaccines. The companies making these vaccines are testing for potency and making sure the vaccine does not become contaminated with other diseases.
Unfortunately, there are only a few companies and veterinary supply outlets selling single vials of Marek’s vaccine to small flock owners. The individual vials contain 1,000 to 5,000 doses of vaccine. This vaccine arrives refrigerated with cold packs as it must never be allowed to warm up while in storage. If it arrives warm, it is no longer effective, and the seller should be called to get replacement product. The vaccine must be refrigerated until it will be used.
The other type of vaccine, which is frozen and kept in liquid nitrogen tanks, is available for hatcheries. However, this type of product is not practical for most small flock owners.
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